It's silly to complain about pokémon with minor differences when cases like the costumed Pikachu exist. I think it's fair to assume that the lack of variety within pokémon species is simply a technical limitation.
And why is it okay to draw pokémon more "realistically" EXCEPT when it comes to human features? Many pokémon are meant to be human-like yet people are only allowed to focus on everything BUT those traits. Pikachu is a bad example for this, of course, but it gets the point across. Many of you would complain even if it was a Jynx or Lopunny.
TL; DR: stop being so literal-minded.